using System;
using static System.Console;
using System.Linq;
using System.Collections.Generic;

class Program
{
    static int NN => int.Parse(ReadLine());
    static long[] NList => ReadLine().Split().Select(long.Parse).ToArray();
    public static void Main()
    {
        Solve();
    }
    static void Solve()
    {
        var n = NN;
        var d = NList;
        Array.Sort(d);
        var ans = new char[n];
        for (var i = 0; i < n; ++i) ans[i] = (char)('A' + d[i] % 26);
        WriteLine(string.Concat(ans));
    }
}